China-Bozhong Vacuum

The Roots vacuum pump (i.e. Roots pump) is a kind of circumgyration and cubage transformable vacuum pump.It is evolved from the Roots fan. According to the different work situation, the Roots pump can be classified into low vacuum Roots pump which discharges to the atmosphere directly, the middle vacuum Roots pump(also calls mechnical adding pressure pump), and the high vacuum Roots multilevel vacuum pump.In general,the characteristcs of the Roots pumps are as bellow：

Have the higher speed in the wider compressure scope；
Start and can work at once；
Insensitive to the dust and steam that included in the pumping air；
Without oil in the casing cavity, so it is not necessary to lubricate the rotor；
Low libration，the rotor dynamic ballance is better, and without discharge valve；
Low drive power and little mechnical friction expense；
Structure compact and need small space；
Operation maintaining cost is very low.

So the Roots pump is extensively used in metallury,petrolchemical,paper making,foodstuff,electric industry ect..


Homepage	the Roots vacuum pump work principle
The Roots vacuum pump (i.e. Roots pump) is a kind of circumgyration and cubage transformable vacuum pump.It is evolved from the Roots fan. According to the different work situation, the Roots pump can be classified into low vacuum Roots pump which discharges to the atmosphere directly, the middle vacuum Roots pump(also calls mechnical adding pressure pump), and the high vacuum Roots multilevel vacuum pump.In general,the characteristcs of the Roots pumps are as bellow： Have the higher speed in the wider compressure scope； Start and can work at once； Insensitive to the dust and steam that included in the pumping air； Without oil in the casing cavity, so it is not necessary to lubricate the rotor； Low libration，the rotor dynamic ballance is better, and without discharge valve； Low drive power and little mechnical friction expense； Structure compact and need small space； Operation maintaining cost is very low. So the Roots pump is extensively used in metallury,petrolchemical,paper making,foodstuff,electric industry ect..
The Roots pump's work principle： The Roots pump's structure refers to the right picture. In the pump cavity，there are two rotors which shape is like the number "8". The two rotors are set upright on a pair of parallel shafts, and they move synchronized in reverse direction and drive by a pair of gear wheels which transmission ratio is 1. Between the rotors, the rotor and the inner wall of pump must keep a definite distance，to achieve the high speed running. Because the Roots pump is a kind of pump without inner compression, the compression ratio is usually very low. Hence when the high and middle vacuum Roots pumps work, they need add a fore pump. The Roots pump's limited vacuum is determined by its structure and the production precision, and also the fore vacuum pump's limited vacuum .In order to improve the Roots pump's limited vacuum, several Roots pumps can be used connecting in series. The Roots pump's work principle is similar with the Roots fan. Accompanying the rotor turning continually, the gases is pumped from the inlet mouth into the space "v0" between the rotator and casing, further pumped out through the outlet mouth. Because the "v0"space is completely closed after the suction, the gases in the casing is not compressed or inflation. But when the top of rotor passes the edge of the outlet mouth, and the space "v0" is connected with the discharge side, the gases compression of the discharge side is higher than the space "0", so a lot of gases re-back to the space"v0", that makes the gases compression becomes higher suddenly. Along with the rotor continually turning, the gases are pumped out of the casing. See the picture: It is the suction process of the rotor turning from 0°to 180°. At the position of 0°（Picture a），the low rotor closes the gases inhaling from the inlet mouth in volume of the space "v0". When turns to the position of "45°（Picture b），the cavity is communicated to outlet mouth. Cause the compression of the discharge side is much higher, so a lot of gases re-back. While the rotor turns to position of 90°(Picture c)，the gases are closed by the low rotor and the re-back gases are pumped outside all together. At the moment, the up rotor also closes the gases from inlet mouth in volume of space "v0". As the rotor continually turns to "135°"（Picture d），the gases closed by the up rotor is communicated with the outlet mouth, repeating the process above. The position of "180°"（Picture e）is as same as the"0°". The rotor's main shaft rotates once time, the pump four times volume of the space "v0"(Picture a).